The relationship of the decline in intellectual abilities in normal and pathological aging to structural changes in the brain is not well understood. Computerized axial tomography (CAT Scan) is a non-invasive technique which provides a relatively direct and quantifiable measure of cerebral atrophy. This study will investigate the association between performance on intellectual tests and the degree of cerebral atrophy as measured by CAT scan, in individuals who are suspected of primary degenerative dementia (Alzheimer's Disease). The hypothesis being investigated is that the degree of cerebral atrophy is related to the severity of cortical dysfunction as measured by intellectual tasks. Patients who are receiving diagnostic evaluation for suspected dementia, and who are in good physical health with no evidence of major focal cerebral lesion, will be sequentially selected to participate in the study. Atrophy scores will be calculated from CAT scan measurements, and current psychological test data will be obtained from all subjects, sampling performance over a range of skills. Statistical analyses will be used to determine the interrelationships among age, cerebral atrophy, and intellectual functioning. Systematically investigating these relationships will help to clarify the relationship of structural changes in the brain of Alzheimer's Disease.